1. 1 Performance aspects of the instrument M. Bertaina Univ. Torino & INFN EUSO Balloon Phase A Review Meeting, CNES Toulouse, February 2 nd 2012

2. 2 Functional Requirements R-4.1-1 Background imaging The Instrument shall image the UV sky background in the bandwidth used by the JEMEUSO mission observational technique. The background includes star light, airglow, light from artificial sources. R-4.1-2 Detection of EAS The Instrument shall trigger, detect and image EAS with energy above 10 18 eV that might develop in the field of view. R-4.1-3 Technology demonstrator All key components and the relative sub-assembly items should be tested according to the configuration foreseen for the JEM-EUSO mission. This is needed to test the JEM-EUSO detection technique. From: EUSO BALLOON INSTRUMENT Technical Specification document Document: EUSO-TS-INST-206-LAL V1.0

3. 3 On the Sky Background Nightglow background: 100 - 500 photons/m 2 /ns/sr Sakaki, BABY, NIGHTGLOW, Tatiana increases by ~1.5 with clouds Airglow (~100 km height): 250 - 600 photons/m 2 /ns/sr Moon phases (<25%): <100 ph/m 2 /ns/sr 500 1000 2000 From Tatiana Universitetsky Satellite.  and  = large cities ph/m 2 /ns/sr Background measurements with coarse resolution (~200 km FoV)

4. 4 BABY vs Tatiana: with reduced FoV higher fluctuations are expected O.Catalano et al., NIMA 480 (2002) 547 Balloon trajectory EUSO-Balloon: a)will have finer resolution at ground (~200m) b) will implement a control on background variations to keep a stable trigger rate (~7 Hz)

5. 5 SWITCHES LOGIC AND BRIGHT EVENTS (TLEs) TLEjet Power10 4 W Duration0.4 s Radius40 km Height in atm. Troposphere NO SWITCHES WITH SWITCHES THE SIGNAL HAS BEEN SAMPLED: THE INTERVAL BETWEEN 2 GTUs IS 1 ms!!! 250 pC 0 s 0.4 s 250 pC The logic of switches of EUSO-Balloon will be tested to verify: a)Capability of protecting the detector from bright events b)Measure their light curve and intensity

6. 6 The observation principle of JEM-EUSO Simulation of the light profile observed at the entrance pupil (above) and throught the instrument using the ESAF code duration ~ 50 – 150  s

7. 7 PARAMETERS OF EUSO-BALLOON COMPARED TO JEM-EUSO JEM-EUSOEUSO-Balloon Height(km)42040 Diameter(m)2.51 FoV/pix(deg)0.080.25 Pixel@ground(km)0.5800.175 FoV/PDM(deg)3.812 PDM@ground(km)28.28.4 Signal Ratio117.6 BG Ratio10.9-1.8 S/  N 120-10 E thr (eV)3x10 19 1.5-3x10 18 Number of PDM1431 Maximize performance of EUSO-Balloon keeping parameters as close as possible to JEM-EUSO

8. 8 First assessments on the EAS observation by EUSO-Balloon A)Shower simulator SAITAMA Code, version Sato – 2005) B)Ray trace code version Takky – 07112011 C)Flat PDM D)M64 PMT simulation as in JEM-EUSO M64 E)Trigger module as in JEM-EUSO F)Average nightglow background adapted to EUSO-Balloon (1.4 - 2.8 phe/pix/GTU) G)Accepted fake trigger rate ~7 Hz Simulation inputs: R=4.2km R=10km EAS impact point at ground simulated at distances R < 10 km around the Nadir of the telescope.

9. 9 Typical event observable by EUSO-Balloon (1) phe/GTU Time(GTU) Xpix Ypix Xpix Proton: E = 2·10 18 eV  = 49.0   = 213.0  X 0 = 3.0 km Y 0 = 2.9 km phe/GTU Event landing in the FoV

10. 10 phe/GTU Time(GTU) Xpix Ypix Xpix Proton: E = 4·10 18 eV  = 57.5   = 188.7  X 0 = 9.3 km Y 0 = 3.1 km phe/GTU Event landing outside the FoV Typical event observable by EUSO-Balloon (2)

11. 11 GTU = 1GTU = 2 GTU = 3GTU = 4 X(pix) Y(pix) Proton: E = 4·10 18 eV  = 57.5   = 188.7  X 0 = 9.3 km Y 0 = 3.1 km : 1.4 phe/pix/GTU phe Simulation of event (2) GTU by GTU with background

12. 12 GTU = 5GTU = 6 GTU = 7GTU = 8 X(pix) Y(pix) Proton: E = 4·10 18 eV  = 57.5   = 188.7  X 0 = 9.3 km Y 0 = 3.1 km : 1.4 phe/pix/GTU phe Simulation of event (2) GTU by GTU with background

13. 13 GTU = 9GTU = 10 GTU = 11 GTU = 12 X(pix) Y(pix) Proton: E = 4·10 18 eV  = 57.5   = 188.7  X 0 = 9.3 km Y 0 = 3.1 km : 1.4 phe/pix/GTU phe Simulation of event (2) GTU by GTU with background

14. 14 GTU = 13GTU = 14 GTU = 15GTU = 16 X(pix) Y(pix) Proton: E = 4·10 18 eV  = 57.5   = 188.7  X 0 = 9.3 km Y 0 = 3.1 km : 1.4 phe/pix/GTU phe Simulation of event (2) GTU by GTU with background

15. 15 GTU = 17GTU = 18 GTU = 19GTU = 20 X(pix) Y(pix) Proton: E = 4·10 18 eV  = 57.5   = 188.7  X 0 = 9.3 km Y 0 = 3.1 km : 1.4 phe/pix/GTU phe Simulation of event (2) GTU by GTU with background

16. 16 Energy(eV) Integrated N. Events [10 18,E]eV in 10h LEFT PLOT: Trigger efficiency curve for events with impact point inside FoV. RIGHT PLOT: Black, red and blue curves give preliminary results on the performance from a 10 h duration flight for different assumptions of background and cosmic ray flux. 7 Hz/PDM Trigger efficiency (%) Energy(eV) Efficiency=1 & 1.5 x Aug. flux Efficiency=1 & Auger flux EB & A.fl. & =1.4 phe EB & 1.5xA.fl. & =1.4 phe EB & A.fl. & =2.8 phe EUSO-B. & =1.4 phe/pix/GTU EUSO-B. & =2.8 phe/pix/GTU ● 80 Hz fake trig. o 7 Hz fake trig.

17. 17 CONCLUSIONS EUSO-Balloon will IMAGE the UV sky background (star light, airglow, TLEs, artificial lights) in the bandwidth used by the JEMEUSO mission observational technique. All key components and the relative sub-assembly items will be tested according to the configuration foreseen for the JEM-EUSO mission. In particular the trigger scheme and its capability to cope with the variable sky conditions (EXTREMELY IMPORTANT). A first simulation study has been performed to understand the effective energy threshold of EUSO-Balloon and its possibility to detect showers in a 10h flight. Results confirm the capability of the instrument of detecting primary cosmic rays of energy E>10 18 eV. Due to the low cosmic ray flux the detection of a couple of events will require few days exposure time (dependent on the sky background condition), therefore the detection of the first air shower from the edge of the space will most probably require more than one flight.